1. Field of the Invention
The invention generally relates to incubation processes, and specifically microbial-based aerobic incubation processes to produce high quality protein concentrates, including products made therefrom and use of such products in the formulation of nutrient feeds.
2. Background Information
In 2008, approximately 28% of the world's wild, marine fish stocks were overexploited and 52% were fully exploited, even as the demand for per capita consumption of fish and shellfish products have increased with the increasing human population. With dwindling wild fish stocks, in an effort to meet this increased demand, commercial aquaculture production has increased dramatically. However, one of the primary constituents of dietary formulations for aquaculture, fish meal protein, is also derived from wild capture fisheries. It is estimated that at least 6.7 mmt of fish meal will be required to support commercial aquaculture production by 2012. This is clearly an unsustainable trend.
Lower cost, more sustainable plant-derived sources of protein have been used to partially replace fish meal in aquaculture diets. Defatted soybean meal (SBM, 42-48% protein) has commonly been used to replace up to 20% of total protein in grower diets for several species, while soy protein concentrate (SPC, 65% protein) has been tested successfully at higher total protein replacement levels, largely governed by the trophic status of the species. These soybean products provide high protein and relative good amino acid profiles, but are still deficient in some critical amino acids (e.g., taurine) required by carnivorous marine fishes. SPC can be used at higher levels than soybean meal, primarily because the solvent extraction process used to produce SPC removes anti-nutritional factors (e.g., oligosaccharides) and thereby increases protein bioavailability. In addition, a thermal step has been used to inactivate heat-labile antigenic factors. The primary limitations of the current solvent extraction process are its cost, the lack of use for the oligosaccharides removed in the process, and quality issues that frequently limit inclusion to 50% of total protein in the diet. Further, processing of soy material into soybean meal or soy protein concentrates can be environmentally problematic (e.g., problems with disposal of chemical waste associated with hexane-extraction).
Corn co-products, including dried distiller's grains with solubles (DDGS), have also been evaluated in aquaculture diets at fish meal replacement levels of up to 20%. DDGS has lower protein (28-32%) and more fiber than soy products, but is typically priced at ˜50% of the value of defatted soybean meal. Some ethanol plants have incorporated a dry fractionation process to remove part of the fiber and oil prior to the conversion process, resulting in a dry-frac DDGS of up to 42% protein. While this product has been used to replace 20-40% of fish meal in aquaculture feeds, there remains the need for a higher protein, more digestible DDGS aqua feed product. Such a product would be especially attractive if the protein component had higher levels of critical amino acids such as taurine, lysine, methionine, and cysteine.
Therefore, a plant-derived protein source which is cost-effective and “green,” and that is of a high-enough quality to fully or substantially replace more of the fish meal in an aquaculture diet is needed.